The invention relates to the construction of paperboard cartons for dispensing rolls of plastic film, foil, wax paper, etc. More specifically, the invention relates to a paperboard carton having a plastic cutting blade (e.g. polystyrene), and a method of constructing the carton and attaching the plastic cutting blade to the carton.
It is well known to dispense plastic films, wax paper, aluminum foil and other film materials from a paperboard carton. Normally, these paperboard cartons are formed from die-cut paperboard blanks which are glued and folded to form an elongated roll storage cavity. A lid is connected to the carton along a fold line between a back panel and the lid, such that the lid pivots about the fold line from an open position to a closed position. The lid normally has a front lip that nests adjacent a front panel of the carton when the carton is closed. Alternatively, the lid has a flap that folds inside the front panel to close the carton.
In most paperboard cartons, a serrated metal cutting blade is provided to cut the film or foil. The metal cutting blade is typically attached along the top edge of the front panel, although it is known in the art to attach the metal strip to the inside surface of the front lip. With either arrangement, the serrated edge is exposed in order to allow the user to tear the web along the serrated edge. It is known in the art to cover the serrated edges for shipment, perhaps using a removable cover strip over the serrated edge.
The serrated metal cutting blades are typically attached to the paperboard carton by stamping the serrated metal blade at a plurality of points onto the paperboard carton blank at the appropriate location. Such stamping techniques have been found much more reliable than adhesive, especially inasmuch as the width of the metal strips is typically about xe2x85x9c of an inch and thus provides insufficient surface area for effective use of adhesive.
The present invention was developed in an attempt to increase production speeds above those now possible for paperboard cartons using metal cutting blades.
The invention is a paperboard carton that uses a plastic cutting blade mounted to the inside surface of the front lip of the lid. The plastic cutting blade is preferably approximately {fraction (20/1000)} of an inch thick polystyrene which is die-cut to form teeth along one of its longitudinal edges. Each end of the polystyrene cutting blade preferably has aggressive teeth which are larger in size than the remaining teeth of the serrated edge to help initiate tearing of the web material.
One of the primary advantages of the invention is that the plastic cutting blade can be securely applied to paperboard carton blanks at a much faster production rate (e.g. approximately 150 units per minute) than the stamped metal cutting blades of the prior art. The plastic strip is preferably attached to the paperboard carton blanks using commercially available print finishing systems in which a feeding mechanism has been modified to accommodate feeding of the elongated plastic cutting blades. Hot melt adhesive is preferably used to secure the plastic cutting blade to the inside surface of the front lip of the lid. It has been found that the use of hot melt adhesive is particularly well suited for high production speeds. At reduced speeds, however, other means of adhering the plastic cutting blade to the paperboard carton blank (e.g. heat sealing, ultrasonic sealing, providing pressure-sensitive adhesive on the plastic cutting blade, etc.) may be suitable. In order to ensure adhesion of the plastic blade to the inside surface of the front lip of the carton as well as ensure the structural integrity of the plastic cutting blade, the width of the blade is preferably approximately one inch such that the plastic cutting blade substantially covers the entire inside surface of the front support lip on the carton lid. Another advantage of the invention is that the plastic cutting blades are somewhat safer to handle during the manufacturing processes, as well as by the end user.
In addition, the use of plastic cutting blades simplifies the recycling of paperboard cartons. Metal cutting blades complicate pulping procedures when the paperboard cartons are recycled in a batch along with other paper products. For example, it is normally necessary to remove metal cutting blades prior to or during the pulping process in order to protect recycling equipment. The use of plastic cutting blades eliminates this problem.
Another advantage of using a plastic cutting blade is that static is generated by the plastic cutting blade as the web is tom. This makes the film stick to the front of the carton, and it is therefore easier to grab the web for the next tear. Many prior art cartons used a small sticker to accomplish the same result.
Other advantages and objects of the invention may be apparent to those skilled in the art upon inspecting the following drawings and description thereof.